Golf ball manufacturers have been able to vary a wide range of playing characteristics, such as compression, velocity, and spin, by altering the composition of the golf ball. Depending on the layer and desired performance, golf ball layers may be constructed with a number of polymeric compositions and blends, including polybutadiene rubber, polyurethanes, polyamines, and ionomers. For example, golf ball manufacturers have been using ethylene-based ionomers for golf ball component materials because of their durability, rebound, and scuff resistance characteristics. These ionomers are distinguished by the type of metal ion, the amount of acid, and the degree of neutralization.
Those of ordinary skill in the art are aware that increasing the neutralization of ethylene-based ionomers during manufacturing reduces the processability of the material. In fact, depending upon the cation(s) present, once the neutralization is greater than about 60 percent, the melt flow index of the ionomer is decreased to the point that the material does not flow at all under normal processing conditions. As a result, commercially available ethylene-based ionomers are generally only partially neutralized.
More recently, however, highly-neutralized polymers (“HNPs”) have been found to be suitable materials for golf ball layers due to their excellent performance properties. The acid groups in these polymers are typically neutralized to high levels, e.g., greater than about 80 percent. However, the high neutralization levels still present difficulties under normal processing conditions. In addition, customization of HNPs is difficult because the specific base resins used to make the HNPs are not generally commercially available.
Accordingly, there remains a need for ionomer compositions that are neutralized at high percentages, but in a manner that still allows the use of the resultant polymer compositions in golf ball components. Advantageously, the compositions of the present invention may be made into golf ball layers having enhanced resiliency, durability, and compression.